What to Expect When Starting Acyclovir
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Introduction
Acyclovir is an antiviral medication used to treat infections caused by herpes viruses, including genital herpes, cold sores, chickenpox, and shingles. It works by stopping the virus from replicating, which reduces the severity and duration of outbreaks. Most people experience significant symptom relief within a few days of starting treatment.
Week-by-week timeline
Starting Treatment
Take your first dose as prescribed. For active outbreaks, antiviral effects begin quickly. You may notice mild nausea or headache as common early side effects. Drink plenty of water, as acyclovir requires good hydration for kidney clearance.
Symptom Improvement
Outbreak symptoms (pain, itching, lesions) should begin to improve. Healing is typically faster than without treatment. Continue taking every dose on schedule — missing doses reduces effectiveness.
Completing Acute Treatment
For acute episodes, the full course is typically 5-10 days. Lesions should be healing or healed. If on suppressive therapy, you are establishing a daily routine.
Suppressive Therapy Baseline
If on daily suppressive therapy, you should notice a reduction in outbreak frequency. Side effects are generally minimal with long-term low-dose use. Kidney function is monitored if on high doses.
Long-Term Assessment
Continued suppressive therapy significantly reduces transmission risk and outbreak frequency. Discuss with your provider whether ongoing suppression is right for you.
When to call your doctor
Contact your healthcare provider if you experience:
- Severe skin rash, hives, or difficulty breathing (allergic reaction)
- Decreased urination or signs of kidney problems (swelling, unusual fatigue)
- Confusion, hallucinations, or seizures (rare neurological effects)
- Severe abdominal pain or bloody stools
- Yellowing of skin or eyes (jaundice)
- New or worsening symptoms after completing treatment
Tips for getting started
Take acyclovir with a full glass of water and stay well hydrated throughout treatment. If taking multiple doses daily, space them evenly throughout the day. For genital herpes suppressive therapy, use condoms even when outbreak-free to further reduce transmission risk. Store at room temperature away from moisture and heat.
Frequently asked questions
More about Acyclovir
References
- [Regulatory] FDA Label: Acyclovir Capsules, Tablets https://www.accessdata.fda.gov/drugsatfda_docs/label/2005/018828s031lbl.pdf Accessed 2026-03-01.
- [Regulatory] NIH MedlinePlus: Acyclovir https://medlineplus.gov/druginfo/meds/a681045.html Accessed 2026-03-01.
- [Regulatory] CDC: Genital Herpes Treatment Guidelines https://www.cdc.gov/std/treatment-guidelines/herpes.htm Accessed 2026-03-01.
Written and fact-checked by PrescriptionDrugs.org Editorial Team
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